In what circumstances do scientists use observational research and opinion based research?

Observational research is used in early stages of scientific research because it gives us a rough estimate and a general idea at what variables should be look at when we're trying to discover something new.

Opinion based research works through the same principle, someone who is an expert in a field can tell us what does he think could be researched next. Both of these pieces of information are only used as a general idea and not as something definitive.

1.from liquid state to gaseous state is evaporation 3.solid to liquid is melting 5. solid to gaseous state is sublimation 6. gas to solid state is decomposition 7. a change of state is known as the states of matters

Heating it up with cause a quicker reaction time